Brakes Get Wired

Electronic braking systems are about to make their North American debutAlthough commonplace in European truck operations, "brake-by-wire" technology has yet to gain much traction in the U.S. That could soon change when Freightliner Corp., in concert with Meritor WABCO, lifts the veil on the first EBS system for heavy-duty trucks early next year.Still in its embryonic stages, EBS technology is considered

Electronic braking systems are about to make their North American debut

Although commonplace in European truck operations, "brake-by-wire" technology has yet to gain much traction in the U.S. That could soon change when Freightliner Corp., in concert with Meritor WABCO, lifts the veil on the first EBS system for heavy-duty trucks early next year.

Still in its embryonic stages, EBS technology is considered by many to be the next advance in heavy-duty braking, providing fleets with important advantages in brake balance, stability, and control. EBS uses electronic impulses, rather than air, to send a brake signal. Brake actuation components, however, remain the same: compressors, air dryers, air reservoirs, foundation brakes, slack adjusters, and brake chambers.

Here's how it works. When a driver hits the brakes, an electrical signal travels from the brake pedal transmitter to the EBS electronic control unit. This signal informs the EBS of the desired amount of deceleration selected by the driver. Sensors then measure parameters such as axle load, wheel speed, and lining wear, and send out the appropriate braking pressure on each wheel or axle of the tractor and trailer. All within a fraction of a second.

If there is ever a malfunction, the system reverts to the basic pneumatic braking system. Current government regulations require that initial versions of EBS be equipped with a complete pneumatic system as a backup.

"EBS works," says Dave Hammes, director of international sales and business development for AlliedSignal Truck Brake Systems and chairman of The Maintenance Council task force evaluating EBS performance issues. "The major obstacles in both Europe and the U.S. are government requirements that do not allow an independent EBS."

That's the main beef of truck fleets. "If electronic braking systems are so great, why do we have to buy both?" queries Larry Strawhorn, vp-engineering for the American Trucking Assns. Although he understands the need for caution, Strawhorn says that fleets are being saddled with increased complexity, weight, and cost. "Fleets have all the old problems -- and the new ones, too," he says.

Don't look for that to change anytime soon. "We're planning to do research in 1998," says George Soodoo, group leader for the National Highway Traffic Safety Administration's vehicle dynamics division. Such research would be in advance of any rulemaking proceeding.

Although nobody is pushing to kill the redundancy requirement just yet, manufacturers do recognize that it adds to the fleet frustration index. "We still have spaghetti under the dash," says Hammes. "All the connections and air lines add weight and cost that could be eliminated in a pure EBS system."

But most industry experts agree that a pure system is still years away. "We are starting with a highly redundant belt-and-suspenders type of product," explains Dennis L. Sandberg, director of electronic products for Meritor WABCO Vehicle Control Systems. "We have to make certain the system performs as we expect it to. As an industry, we're offering a pretty costly system compared to where EBS can take us down the road. For now, we have to address how we would stop the truck if we had a full electronic blackout."

The challenge is to provide the same braking performance, while at the same time encouraging fleets to get the electronic brakes repaired as soon as possible, according to Tony Moore, manager of axle and brake systems for Freightliner Corp. For now, Freightliner has set tled on a dual electronic system that monitors the brakes. In the event of a failure, the system reverts to the pneumatic brakes. "It will require more pedal effort to get into the backup mode," Moore says. "But it will provide the same level of performance."

"It takes time to develop a product and make sure it is commercially reliable and durable," says Sandberg.

To get there, manufacturers have spent the last 18 months putting the product into selected fleets and evaluating the performance. Those evaluations have yielded important information. For instance, one technical glitch uncovered was that EBS was affected by the voltage drop when the vehicle was started.

After correcting some of the early problems, the systems have been running "almost flawlessly," reports Moore.

AlliedSignal has tested EBS on vehicles for over 10 years, according to Jim McClelland, director of marketing for electronic control systems. Evaluations have included complete brake systems as well as "dash control only" subsystems. "Based on our testing and fleet feedback," says Mclelland, "fleets van see the promise of improved vehicle-systems functionality. This includes improved brake control, improved vehicle Drive Stability Control, roll over protection, and predictive diagnostics. The key is to optimize performance with fleet value and payback, while minimizing system complexity and cost."

ATA's Strawhorn frets that manufacturers are spending more money developing EBS, to the detriment of advances in the basic pneumatic system. "We haven't argued that EBS isn't the way to go," he says. "But we're kind of stuck with the existing system until the new technology is ready."

A close look at that technology reveals a braking system that gives drivers more control because it fires off electronic impulses. They get instant response, rather than having to wait for the compressed air signal to weave its way through the serpentine hoses. EBS auxiliary systems can also detect brake fade and notify drivers if wear levels become critical. In addition, the control over braking is more predictable, regardless of equipment loads, thus shortening stopping distances and improving vehicle stability.

"EBS can also do things like load-proportion braking," says Rick Youngblood, market development manager for ABS and EBS for Eaton Truck Components Ops. - Americas. "If a vehicle is lightly loaded, the brakes proportion more braking power to the steer axle. If the load is heavier, they proportion more to the rear."

Other performance advantages include: shorter stopping distances; improved vehicle stability and control; longer lasting linings that wear more evenly; integrated retarder actuation; better brake system timing and balance; equalized braking at each wheel end; and reduced amount of plumbing.

In longer vehicle combinations, EBS will also enable devices to suppress rearward amplification of the rear-most unit.

Manufacturers expect to see benefits in maintenance as well. Right off, EBS eliminates the numerous air hoses that travel from the cab to the brake chambers. That means less plumbing and fewer potential leak points.

With its improved diagnostics, EBS can measure key performance characteristics such as brake stroke, brake lining wear, and temperature. "As a result, fleets can schedule brake jobs to change everything at once," says Dave Engelbert, engineering manager for research and development at Midland-Grau Heavy Duty Systems.

Even with its advertised benefits, how the system works in the real world remains to be seen. "Manufacturers have full faith in the system when they run it in a controlled test environment, says Strawhorn. They get all puckered up, however, when they turn them over to 'us' -- and 'us' is a lot of different shapes and sizes."

Indeed, one of the chief fears expressed by the manufacturing community is that EBS performance and reliability can be compromised by using cheap harnesses and poor grade wiring.

For their part, manufacturers are looking for real-world results to continue to refine brake by wire. "We'll sell the systems at a loss if we can get the product out in the fleets and get information back on its performance," says Engelbert.

As manufacturers glean more operating data, future generations of brake by wire likely will do more and cost less.

That points to a reduction in the level of redundancy. "Right now we have 100% redundancy," says Sandberg, a level "that can't be there for the long term. We have to look at areas where we can take redundancy, parts, and complexity out without compromising vehicle safety and reliability."

But whether manufacturers will ever be able to completely eliminate redundant systems is an open question. Even if they do, "there is extra cost in isolated batteries and back-up electrical systems that would be needed to ensure uninterrupted power to the brakes," according to Eaton's Youngblood.

As work progresses, manufacturers hope to hang additional functions and features on ABS. Features such as lining wear sensors, and stability control systems that will sense steer-axle angle and yaw rates all likely will be merged into EBS. Also, look for load detection sensors, low pressure reservoir monitoring, brake temperature monitoring, and brake stroke sensors.

AlliedSignal's Hammes knows this must be a cooperative effort. "We must work closely with fleet customers and with the federal government to prove that EBS does work, and to help train drivers and mechanics in the proper operation of the system."

ATA's Strawhorn agrees. "I hate to throw cold water on the technology because in the long run it makes sense. But for the short term..." his voice trails off. "It cries out for a joint effort involving government, fleets, and manufacturers through a cooperative initiative such as Tomorrow's Truck."

Today, EBS is only months away from true commercial availability. Then the real judging begins.

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